The rebel Lib Dem says the policy is "Dickensian in its social divisiveness" and "victimises the most marginalised".

Campaigners protest against the bedroom tax in Trafalgar Square before marching to Downing Street on 30 March 2013. Photograph: Getty Images.

One thing to look out for during today's Commons debate on the bedroom tax, called by Labour, will be the number of Lib Dems who vote against the measure. At its recent conference, the party backed a motion calling for "an immediate evaluation of the impact of the policy" and for "a redrafting of clear housing needs guidelines in association with those representing vulnerable groups including the disabled, elderly and children."

Until new guidelines are in place, it argued that there should be no withdrawal of housing benefit from those on the waiting list for social housing and that there should be an exemption for those who "temporarily have a smaller housing need due to a change in their circumstances, but whose need will predictably return to a higher level (e.g. whose children will pass the age limits for separate rooms within that period)".

But some senior figures went further, with Shirley Williams describing it as "a big mistake" and Charles Kennedy commenting: "I didn’t support it in the Commons and I’m not going to support it here."

One Lib Dem MP who will be walking through the division lobby with Labour is Andrew George. Here's the statement his office have just sent me, I've highlighted one particularly striking section.

If Government Ministers are so confident that this is the right policy then they should come down to meet some of my constituents who are affected by it and look them in the eye as they attempt to justify it.

I fully understand that in a Coalition Government Liberal Democrat Ministers are expected to hold their noses as they back a Tory policy. But let it be said, the Liberal Democrats should reverse this policy at the first opportunity.

The spare room penalty/bedroom tax victimises the most marginalised in our communities, it undermines family life, it penalises the hard working low paid for being prepared to stomach low paid work, it masks the excessive cost and disruption caused to those disabled people who have to move from expensively adapted homes and is Dickensian in its social divisiveness.

I hope that those Ministers who live in multiple spare room mansions and who strenuously oppose the Liberal Democrat "Mansion Tax" will be prepared to look the victims of this policy in the eye. [Emphasis mine.] Even where those affected are prepared to move to up root themselves from a long standing family home to a smaller property they tell me they can't find anything within 20 - 30 miles. So to escape the bedroom tax they would have to move many miles from their community, their work place, local school, family and social networks, church etc. and re-establish themselves in a place which they may consider to be completely alien. Or of course they could choose a property in the private sector and cost the taxpayer more!

If the policy isn't based on class prejudice it is based on indifference to the most vulnerable families in our communities.